Mining core
Rock Mechanics
5 self-contained study topics — notes, diagrams, formulas, and worked examples for exams and GATE.
Topics
- Stress in Rock MassVertical stress σ_v = γH increases with depth; horizontal stress K_0σ_v often exceeds unity in Indian shield regions. Excavation redistributes stress — concentration at tunnel crown and pillar corners drives support design.
- Rock Strength CriteriaMohr-Coulomb τ = c + σ tanφ governs shear failure on planes; Hoek-Brown captures rock mass non-linearity via GSI and σ_ci. Triaxial tests yield c and φ or Hoek-Brown parameters for slope and tunnel design.
- Rock Mass ClassificationRMR and Q-system classify rock mass from field ratings to predict support and stand-up time. GSI visually estimates Hoek-Brown parameters — all three require honest discontinuity survey, not default mid-range values.
- Support Systems in ExcavationsExcavation support combines rock bolts, shotcrete, and sets sized from RMR/Q class — bolt capacity limited by tension, pull-out, or shear. Active pre-tensioned bolts load rock immediately; passive bolts activate with deformation.
- Slope Stability in MinesMine slope stability uses limit equilibrium FS = resisting/driving moments on circular or planar slip surfaces. Bishop method accounts for interslice forces — design FS typically ≥ 1.2–1.3; piezometric rise after monsoon is critical in Indian open pits.